WITH the whiff of a fifth Wimbledon singles title in the air, grass court predator Serena Williams cut down defending champion Petra Kvitova to move ominously into the semi-finals yesterday.

The 30-year-old American, who still looks unstoppable when in full flow on a grass court, wheeled out the heavy artillery to crack down 13 aces in a 6-3 7-5 victory that significantly raised the bar in a disappointing women's tournament.

Fourth-seeded Czech Kvitova, who boasts some lethal weaponry of her own, fought fire with fire to stay in contention but was eventually dethroned in a high-quality clash which marked Williams's first taste of life under the Centre Court roof.

"You can't play a defending Wimbledon champion or Grand Slam champion and not elevate your game," Williams said.

"I had to weed out the riffraff and just get serious."

The men's draw finally got back on track as the five fourth-round matches were finished 24 hours later than scheduled despite the best efforts of a nonexistent UK summer.

For a change it was all quite tame for home favourite Andy Murray, who dispensed with the theatrics to ease past Marin Cilic into the quarterfinals for a fifth year in a row.

On the day the women's last eight normally take centre stage at the grass court Grand Slam, Murray returned at midday to finish off Croatian Cilic 7-5 6-2 6-3 to fuel hopes of a first home men's winner at the championships since 1936.

The fourth seed was again held up by rain for a while but took advantage of a bright slot in the murky skies to dispatch Cilic with a minimum of fuss. Murray will face Spain's David Ferrer in the quarterfinals in a repeat of their Roland Garros clash after the seventh seed overcame Argentina's Juan Martin del Potro 6-3 6-2 6-3.

Florian Mayer and Philipp Kohlschreiber continued Germany's impressive showing, both reaching the quarterfinals.

Mayer finished off Frenchman Richard Gasquet 6-3 6-1 3-6 6-2 and will face defending champion Novak Djokovic today, while Kohlschreiber ended the run of American qualifier Brian Baker to reach his first Grand Slam quarterfinal in which he will play the French showman Jo-Wilfried Tsonga. Tsonga was the last player through, reeling in American Mardy Fish to win 4-6 7-6 6-4 6-4 in a stop-start tussle.

With nine of the past 12 women's singles titles going to either Serena Williams or sister Venus, the scratching of another name on the Wimbledon trophy, as Kvitova did last year, is regarded as a personal affront by the siblings.

While the regular WTA tournaments no longer fire Serena's engines, she comes alive at the business end of Wimbledon and after some patchy performances she is now favourite to reclaim family honour on Saturday.

After saving a set point at 4-5 in the second set, she then drew level at 5-5 with a point of raw brutality.

With Kvitova stranded at the net, Serena had open water either side of the Czech but elected instead to belt the ball straight at her opponent. Amazingly, Kvitova got it back but the American then swatted away the loose ball.

Two games later it was all over - Serena letting out a roar that nearly took the roof off Centre Court.

Meanwhile Angelique Kerber yesterday defeated fellow German Sabine Lisicki, the conqueror of Maria Sharapova, in a nerve-racking battle of the blondes 6-3 6-7 (7/9)

7-5 to reach her first Wimbledon semifinal.

Eighth seed Kerber will face either Polish third seed Agnieszka Radwanska or Maria Kirilenko, the Russian 17th seed, for a place in Saturday's final after getting the better of big-hitting Lisicki.

Wimbledon quarter-finalists Agnieszka Radwanska and Maria Kirilenko suffered frustration on Court One as rain forced their last eight clash to be abandoned late in the final set. With Russian 17th seed Kirilenko serving at 5-7 6-4 4-4 15-0 yet another heavy shower forced the players to scurry to the changing rooms and prompted Wimbledon chiefs to postpone to today.

Second seed Victoria Azarenka reached the semifinals for the second successive year with a 6-3 7-6 (7/4) win over unseeded Austrian Tamira Paszek. Azarenka will face Serena Williams for a place in Saturday's final.